The present invention relates generally to agricultural equipment and more particularly relates to a self-aligning bearing of the type utilized for supporting a shaft having earthworking tools, such as disk blades, mounted thereon.
Rotating earthworking tools such as disk harrow blades are typically supported for rotation with a shaft which in turn is carried by bearings mounted in a support member suspended from an implement frame. The bearings which rotatably support the shaft must be designed to assure that the shaft rotates freely after assembly and to also permit osciallation and dynamic self-alignment of the bearings within the support member during earthworking operations.
During assembly of the shaft, bearings and supports, some misalignment of the shaft or bearings within the support member can result. The bearings must be designed to permit self-alignment during such assembly or rapid failure will occur.
During earthworking operations, oscillation or rocking of the bearing outer race ring within the support can occur as a consequence of several factors. Generally, several supports carry bearings within which a shaft is mounted. The bearing supports are in turn carried by the implement frame. During such operations, various forces are encountered by tools such as disk blades as they work the varying soil conditions and contact objects and obstacles in the ground. These forces create axial as well as radial loadings upon the shaft and bearings and require that the bearings be able to oscillate or rock axially within the support but realign subsequent to exposure to the forces. Further the frame from which the bearing supports are suspended is subjected to vertical and horizontal loadings thereby transferring to the bearing supports axial and radial forces and further requiring that the bearings be designed to absorb axial loadings and be able to shift or oscillate slightly during exposure to the forces.
In U.S. Pat. No. 2,733,648 to E. W. Todd, there is provided a bearing and support that permits misalignment of the support relative to the bearings during assembly. Such misalignment is tolerated through the use of spherically-formed surfaces between the housing support and the outer race rings which can be assembled with the housing support secured in a position skewed from directly perpendicular to the shaft supported by the bearings.
To permit realignment of the bearings within the support after assembly and during exposure to operating forces, metal supports have been designed to encase or shroud the bearings and seals. An example of such a support can be found in U.S. Pat. No. 3,311,429 to Kocian. This encasing support, however, severely limits the degree of oscillation or wobble of the bearing within the support and thus restricts the ability of the bearing to absorb the operating forces discussed above. Further, contaminates can enter this type of encasement and pack the bearings to more severely restrict oscillation capabilities.
In an attempt to provide a bearing support that permits a greater degree of oscillation or wobble during operation, Fafnir and some other bearing manufacturers have provided bearings with lubriciated spherically-formed surfaces between the housing support and outer race ring. See, for example, the Fafnir bearing, Model GVFD, GVFDR Relubricatable Series. These bearings, however, are capable of only limited dynamic realignment since the outer race ring outer surface is sized for an interference fit with the support member and thus can permit relative movement between the two members only when subjected to significant operating forces. Such an interference fit has been necessary to date to prevent the frictional drag generated between the seal lips and inner race ring from rotating the outer race ring within the spherical housing. Further, since bearings used in earthworking operations are typically exposed to dirt, sand, water and other contaminates, severe damage can occur to the interacting metal parts unless they are maintained in a well-lubricated and sealed manner against entry of such contaminates. No such provision for sealing the interacting spherical surface of these bearings has been made.
In an attempt to prevent the entry of such contaminates into agricultural use bearings, overhanging flanges, such as those illustrated in Todd (U.S. Pat. No. 2,733,648), have been used. The flanges which form gaps with the bearing collars act only as deflectors and do not seal out contaminates. Consequently, as dirt accumulates adjacent to the bearing seal, the seal flexibility is soon lost and metal wear rapidly results causing premature bearing failure.